Cache replacement policy still make sense?

Hello,

Considering today's large disk size (>120G), does a cache replacement
policy still play a important role in the cache performance?

Although a large cache will be eventually filled up with files, many of
the cached files will be expired before the cache is full. Therefore,
simply removing that expired files will make a considerable space for
many future requests, and it does not matter that which replacement
policy (LRU, LFUDA, or GDS) is used. Right?

On the other hand, from the benchmarking results shown in:
http://www.squid-cache.org/Benchmarking/HEAP_REPLACEMENT/index.html
We can see that LRU, LFUDA, and GDS perform similarly. It further
support the argument that a replacement policy is playing a LESS
important role in the Web performance. Am I correct?

But, in the above benchmarking result, I do not understand:
1) the "Millions of requests" in the x axis mean. It is the number of
requests per second? or is the accumulated number of requests?
2) the hit ratios are similar until 4 millions of requests is reached.
Does it mean, at that arrival rate, the cache is full, and the correct
choose of a replacement policy will take effect at that case?

Thanks

Angus Wong
Research student at City University of Hong Kong
Received on Wed Aug 27 2003 - 01:56:39 MDT